JPH0253734B2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Field of Application] The present invention is directed to pipes that are buried underground or hidden with concrete, and which prevent leakage from the buried or hidden locations. The present invention relates to a method for detecting a leakage point, which is necessary when a leakage point occurs and the leakage point must be repaired.

[Prior art and its problems] For example, when a gas leak occurs from a gas pipe buried underground, this gas leaks to the surface through the soil. For this reason, the leakage point is usually found by excavating the area on the ground where the gas odor is strongest, but if the road surface is concrete or there is a structure above the gas leakage point, Gas often leaks to the ground from unexpected directions, and in such cases, even if a gas leak is detected on the ground using the odor and gas detector, it is difficult to locate the leak on the gas pipe. is often difficult.

Conventionally, even in such cases, the method of conducting trial digging in several locations and detecting the leak using an odor or gas detector, or by cutting the piping system in certain sections and performing an airtight test to locate the leak point. This method is adopted.

However, implementing the above method requires a lot of time and effort, making it difficult to respond quickly in an emergency, and the piping system is completely hidden due to buildings located above the gas pipe. In such cases, exploration itself may not be possible.

[Objective of the present invention] From this point of view, an object of the present invention is to propose a method for detecting a leakage point in piping, which can accurately find the leakage point in a short time with less effort.

[Configuration of the present invention] The configuration of the present invention is as follows.

Fill the leaking pipe with inert gas, etc.
Next, by suctioning the inert gas etc. from one end, air is drawn into the pipe from outside the pipe near the leak point, forming an air layer near the leak point in the pipe, and then the oxygen concentration is reduced from one end. The distance from the suction end of the piping to the leak point can be determined by continuously measuring the amount of inert gas, etc. sucked in until the oxygen concentration is detected, and dividing it by the cross-sectional area of the piping. In a method for detecting leakage points in piping that requires the formation of an air layer, inert gas, etc. is sucked in the piping while supplying inert gas, etc. from the opposite end of the piping. A method for detecting leak points in piping.

A specific inspection example of the above method will be explained below.

a. First, valves are installed at both ends of a certain section of the piping that includes the gas leak point (hereinafter referred to as the "inspection section") to shut off the inspection section. However, if there is an existing kettle, etc., you may use it. Note that if there is a branch pipe within this inspection section, the valve at the end of this branch pipe is also closed.

b Next, connect the suction line to one end of the test section using an adapter.

c. Input the diameter and length of all piping in the inspection section individually into the calculator. As a result, the total capacity of the pipe is calculated and stored in the calculator.

d Next, pressurize air into the inspection section from the pneumatic feed line, inspect the amount of pressure drop after a certain period of time, and calculate the amount of leakage in the inspection section based on this data and the total capacity of the piping determined in C. Automatically memorize it in the calculator.

e Next, further air is injected into the inspection section,
Create an atmosphere of air in the soil near the leakage point. The press-in amount is automatically set based on the leakage amount determined in step d. However, this measure should not be carried out if the pipe is exposed to the air, but should be carried out if the pipe is underground or if the conditions near the leak point are such that an atmosphere of leaked gas can easily be created.

f Next, the test section is filled with inert gas, and the test section is replaced with the inert gas.

g Next, inert gas is sucked in from within the inspection area through the suction line, and air is sucked into the pipe from the leak location to create an air layer inside the pipe.

The suction time is automatically set based on the leakage amount determined in step d.

h. Once an air layer is formed in the pipe, suck inert gas through the suction line again and supply inert gas from the end of the inspection section. The supply may be stopped after a predetermined amount has been supplied, and then the terminal may be opened to allow air to enter the inspection section.

Alternatively, a dummy tube may be connected to the end of the piping on the opposite side to the suction side, an inert gas or the like may be sealed in the dummy tube, and the inert gas in the dummy tube and the piping may be sucked.

i If the oxygen concentration is detected in the inert gas being sucked, calculate the total amount of inert gas sucked up to that point, divide this by the cross-sectional area of the pipe, and use a calculator to calculate the distance from the suction point to the leak point. This is calculated and displayed on a display, for example on a liquid crystal display, or printed out.

j Once the distance to the leakage point has been determined, identify the location on the piping based on the drawing, excavate it to expose the leakage point, and take necessary measures.

[Example] Hereinafter, an example of the present invention will be described in detail based on the accompanying drawings.

Reference numeral 1 indicates an inspection section within the gas conduit that includes the leakage point P, and valves A and G are attached to both ends of this section, respectively. Also, valves B, C, D, E, and F are attached to the ends of the branch pipes, respectively.

Reference numeral 2 denotes a suction line having an adapter 4 at its tip for connecting to one end of the gas leakage test section 1 and a suction pump 3 attached to its rear end. In addition,
The suction pump 3 of the embodiment is also capable of pumping air into the piping by switching a solenoid valve, and also serves as an air pressure feeding line, but this air pressure feeding line may be provided separately.

Reference numeral 5 denotes a flow meter attached to the suction line 2 to measure the flow rate of gas flowing within the suction line 2.

Reference numeral 6 denotes an O ₂ sensor attached to the suction line 2 in order to measure the oxygen concentration in the gas flowing within the suction line 2.

12 is a cutoff valve attached to the suction line 2 to turn the suction line 2 ON or OFF. In addition, a plurality of solenoid valves are used for switching various circuits.

Reference numeral 13 designates an inert gas injection line for injecting an inert gas (for example, N ₂ ) from a cylinder 14 into the gas leakage test section 1, and is attached to the end of the test section 1 by an adapter. Reference numeral 13a designates an air intake port through which air can be introduced into the inspection section 1 through the inert gas injection line 13.

15 is a pressure gauge attached to the suction line 2 to detect the pressure within the leakage test section 1 via the suction line 2.

16 is based on the input from the flow meter 5 and the O ₂ sensor 6, and calculates the amount of inert gas injected into the inspection section 1 from the start of suction to the time of O ₂ detection in terms of the cross-sectional area of the pipe. By dividing, it is possible to calculate the distance from the suction point to the leak point in the piping, calculate the amount of gas leakage, measure the pressure in the inspection section, and control the control valve to control the amount of compressed air. It is a computing unit that can output signals.

Reference numeral 17 denotes a display device for externally displaying the calculation results of the arithmetic unit 16. Reference numeral 18 indicates a keyboard for inputting various information to the computing unit 16.

Next, an example of use of the above embodiment will be explained.

a First, in leakage inspection section 1, leakage point P
Close valves A and G at both ends of the section including the point, and close valves B, C, D, E, and F.

b Next, the suction line 2 is connected to one end of the test section 1 using the adapter 4. Note that the cutoff valve 12 is open at this time.

c Next, valve A is opened, air is sent into inspection zone 1 by switching from the pump to the solenoid valve, and valve 12 is closed to seal this air, and the initial pressure is measured by pressure gauge 13 after a certain period of time. Measure the pressure drop at and read the amount of leakage from the leakage point P.

d Next, if leakage inspection section 1 is hidden by soil or concrete, check B, C,
Open valves D, E, F, and G, and send air from the pump into inspection section 1 to completely replace the inside of the piping with air. Then B, C, D, E, F, G
After closing the valve, the pressure is further increased, and air flows out from the leak point P to the vicinity, creating an air atmosphere near the P point. Outflow amount is automatically set. Note that there are cases in which the air outflow means is not used and the process moves immediately from c to the next e.

e Next, inert gas is introduced into inert gas injection line 1.
3 into the leak test section 1 to replace the inside of the section with inert gas.

f Next, close valve G, open cutoff valve 12,
The inert gas within the leakage test section 1 is sucked from the suction line 2 using the suction pump 3 to create an air layer X within the leakage test section 1.

g Once the air _layer Continue to detect. However, the inert gas is supplied from the start of suction until a predetermined amount is suctioned, and then from the air suction port 13 in the middle of the inert gas injection line 13.
Let air be sucked in from a.

In addition, a dummy tube 19 is connected to the end of the piping on the opposite side to the suction side through the inert gas injection line 13, an inert gas or the like is sealed in the dummy tube 19, and the dummy tube 19 is inserted into the inspection section 1. It may also be possible to aspirate inert gas.

h The air layer X moves to the O ₂ sensor 6,
When the O ₂ sensor 6 detects the oxygen concentration, the calculator 16 automatically calculates the amount of inert gas sucked up to that point by the cross-sectional area of the pipe, and displays or prints out this data on the display 17. do.

Note that if there is no gas leak between A and G, the oxygen concentration will not increase, so it is determined that there is no leak between A and G.
-F, the entire piping path can be checked by performing the same operation as above.

From the results displayed or printed out as described above, the distance between the suction point and the leak point P can be determined, so all that is left to do is move while measuring on the line of leak inspection section 1 based on the piping drawing, and move to the specified position. If you excavate at this point, you will come across point P.

In the above embodiment, when the enclosed inert gas is sucked, the inert gas is fed from the end of the inspection section 1. The reason for this is that when the leak point P is close to the end of the inspection section, if air suddenly enters without supplying inert gas, the entered air will diffuse inside the pipe and reach air layer X. This is because the presence of this air layer X cannot be detected by the O ₂ sensor 6. For example, if the oxygen concentration in the air layer The concentration is as high as 21%, and the air layer X is absorbed by the diffusion, making it impossible for the O ₂ sensor 6 to detect the air layer X.

FIG. 3 shows an example of detection by the O ₂ sensor 6,
In the above example, when inert gas is introduced from the terminal, the peak X ₁ when air layer X is detected
is clear, but if the leak point P is close to the terminal and the air intake port 13a is fully opened at the same time as suction starts,
This inhaled air diffuses to air layer X, and the dotted line Q
As shown in , peak X ₁ is absorbed.

As a means for feeding the inert gas from the terminal, it may be fed from the inert gas injection line 13 of the terminal as in the embodiment, or it may be fed from the terminal through the inert gas injection line 13 as shown in FIG. A dummy pipe 19 is connected to the dummy pipe 19, an inert gas is sealed in the dummy pipe 19 along with the test section, and the air intake port 13 is sealed.
A may be opened to suck inert gas from the suction line 2.

Although the embodiment has been described as a method for detecting a leakage point in a gas conduit, the present invention is also effective as a method for detecting a leakage point in a conduit other than gas, and is within the scope of the technology. Therefore, depending on the target conduit, the gas sealed in the inspection section and the sensor may change.

[Effects of the present invention] As described above, the present invention first seals an inert gas into a leaking pipe, then sucks this inert gas from one end of the pipe, and creates an air layer sucked from the leaking point. is created in the pipe, then this air layer is sucked in from one end of the pipe, and the amount of inert gas sucked in until the oxygen concentration in the inert gas starts to rise is divided by the cross-sectional area of the pipe. Since the distance to the leakage point can be calculated using the following method, the following effects can be expected.

a. The leakage point can be immediately identified regardless of the burial conditions.

b. Since there is no need to excavate each time, work effort and time are reduced, and leaks in areas where excavation is impossible can be immediately identified.

c. In case of leakage from indoor piping, it can be detected using existing valves, cockpits, etc. without cutting the piping.

d) Leak points can be accurately identified by combining with piping drawings.

e) The device may be simple, does not require special skill to transport or handle, and can be made into a device that can immediately calculate distances using a microcomputer or the like.

f When inert gas is sucked, the inert gas is sent in from the terminal to make the air layer There is no fear that the air layer X will be invaded, and problems such as unmeasurable or undetectable problems and expansion of errors can be prevented.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram of an apparatus for carrying out the method of the present invention;
FIG. 2 is an explanatory diagram of the operation of the present invention, FIG. 3 is an explanatory diagram of an example of oxygen detection by an O ₂ sensor, and FIG. 4 is a diagram of another embodiment in which a dummy tube is attached to the terminal. 1...Leakage inspection section, 2...Suction line, 3...
...Pump, 4...Adapter, 5...Flowmeter, 6
...O ₂ sensor, 12 ... Shutoff valve, 13 ... Inert gas injection line, 14 ... N ₂ gas cylinder,
15...Pressure gauge, 16...Calculator, 17...Display device, 18...Keyboard, 19...Dummy tube.

Claims (1)

[Scope of Claims] 1. Air is sucked into the pipe from outside the pipe near the leakage point by filling an inert gas or the like into the leaking pipe and then sucking the inert gas or the like from one end. to form an air layer near the leak point in the pipe, and then inert gas etc. is sucked in while continuously measuring the oxygen concentration from one end.The inert gas sucked in until the oxygen concentration is detected In the method of detecting a leak point in piping, which calculates the distance from the suction end of the piping to the leak point by dividing the amount of A method of detecting leakage points in piping by sucking inert gas, etc. inside the piping while supplying inert gas, etc. from the side terminal. 2 Connect a dummy pipe to the end of the piping section on the opposite side to the suction side, seal inert gas, etc. in this dummy pipe, and use this dummy pipe when suctioning the inert gas, etc. after forming an air layer. A method for detecting a leakage point in a pipe according to claim 1, which is carried out by suctioning an inert gas or the like inside the pipe.